Heretofore, an oil cleaner has been considered as one which is only to clean lubricating oil, and has been improved in terms of performance of this point.
In fact, recently, in compliance with social requirements for clean environment and with a rapid improvement in filter materials, a deep-layer type filter has been developed which has a considerably higher de-contamination capability than conventional art filters and can provide lubricating oil with an extremely high cleanliness.
In the deep-layer type filter, coarse contaminants are caught by a filter layer located near the inlet and fine contaminants are caught by a filter layer located near the outlet, so that coarse to fine contaminants are caught by different filter layers according to the particle size of contaminants. Therefore, compared with conventional art filters, the deep-layer type filter has an extremely high de-contamination capability so that large amounts of coarse to fine contaminants can be removed, with an extended service life. FIG. 3 is a graph showing changes in flow-rate characteristics Q and pressure characteristics P with time in the de-contamination operation of the deep-layer type filter. As shown in the figure, since contaminants are distributed over the individual layers according to the particle size, a partially clogged state continues for a substantially long period of time, with slight changes in both flow rate and pressure, until a clogging point A at which clogging spreads over the entire filter. After the clogging point A, the flow rate decreases rapidly and the pressure increases rapidly.
However, only a high cleanliness of lubricating oil is not sufficient for machine lubrication. For example, if the flow rate of lubricating oil is decreased by clogging of the filter, the fluid lubricating condition is destroyed, resulting in a boundary lubricating state or a mixed lubricating state, metal abrasion will occur in the lubricated section of the machine and, in the worst case, sticking may result.
Further, if the viscosity of lubricating oil changes due to a change in ambient temperature, the fluid lubricating condition will be destroyed and, in the worst case, sticking will also result.
On the other hand, viewing from the operating condition of the machine, there are inevitable special operating conditions such as start-up operation, heavy-load operation, repeated load operation, and low-speed operation, other than normal operating condition. Under such special operating conditions of the machine, or in transition from normal operating conditions to the special operating conditions, the fluid lubricating condition tends to be destroyed, resulting in metal abrasion and, in the worst case, an accidental sticking.
Therefore, to operate a machine using lubricating oil under the best condition, the flow rate and viscosity of lubricating oil and abrasion of lubricated parts must be monitored. However, as described previously, the prior art oil cleaner had only the oil cleaning function.
Decreased flow rate due to filter clogging may be recovered by replacing the filter. However, since the deep-layer type filter has a considerably higher de-contamination capacity than the prior art filter, it can collect far greater amounts of contaminants in it and, when the collected contaminants reach a specific amount (point A in FIG. 3), the flow rate rapidly decreases. Therefore, it is difficult to determine the time for replacement, and not so easy as is the prior art filter.
The prior art filter also shows flow rate decrease and pressure increase characteristics similar to those shown in FIG. 3 but, since it cannot remove fine contaminants, contamination of lubricating oil increases before complete clogging of the filter. Thus, the degree of contamination of lubricating oil has been checked and both the filter and lubricating oil have been changed.
However, for the case of the deep-layer type filter, because it can output highly cleaned lubricating oil even in the clogged state, if the time for replacement is determined from the degree of contamination, there is a danger of a sudden drop in flow rate of lubricating oil. Therefore, with an oil cleaner using the deep-layer type filter, the filter has been changed periodically at an earlier time to prevent occurrence of such a sudden drop in flow rate, thus resulting in an excessive, uneconomical maintenance.
With a view to obviate all of the prior art defects of oil cleaners, it is a primary object of the present invention to provide an apparatus for supplying lubricated section with lubricating oil with an extremely high cleanliness and monitoring continuously for clogging of a filter, lubricating oil viscosity, and abrasion of lubricated mechanical section, to maintain the best operating condition of a machine.